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Understanding the 5 W’s of Post Op Fever and Its Variations

Post-operative fever can occur as the result of a number of different reasons. To help ease the process of determining the causative factor, a special mnemonic was developed in the 1980’s. This is what we’ve come to know as the 5 W’s of post op fever.

While it’s widely unknown who was responsible for the classic code, these 5 W’s have become an indispensable tool for medical practitioners hoping to determine the reason behind a post-surgical fever.

What exactly are the 5 W’s, what is their importance, and how have they changed throughout the years? Learn everything you need to know about this classic mnemonic by reading through this comprehensive and complete guide to the 5 W’s of post-operative fever

Why a Fever Should Be a Cause for Alarm

What’s so bad about having a fever? Majority of the time, a fever is indicative of an infection of either viral or bacterial origin. In the case of a viral infection, it might not even be necessary to see a doctor. Illness caused by a virus is self-limiting, so all you really need to do is ride it out until it subsides. In the case of a bacterial infection however, taking an antibiotic is a necessary step to effectively eradicate the infection.

Of course, the instances outlined above depict the image of a typical, everyday fever. However a fever that occurs post-operatively can be indicative of something far worse. The reason why you should be particularly alert when it comes to post-op fevers is the fact that they shed light on the status of a person’s healing.

Ideally, an individual should not develop a fever after a surgery or operation. In the event that they do, it’s vital that doctors pinpoint the causative factor in order to resolve the issue and prevent further complications.

This is the rationale behind the 5 W’s of post-operative fevers. The mnemonic represents likely causes for pyrexia at specific times after a person undergoes a surgery. By using this tool as a guide, medical professionals can cancel out potential causes and treat the actual issue causing the fever.

The Traditional Meaning of the 5 W’s

When it was first introduced into the medical realm, the 5 W’s meant wind, water, wound, walking, and wonder drug. These days, several other versions of these W’s are widely accepted, and others still suggest more than just 5 possible factors. Despite the many changes and revisions however, the traditional meaning of the 5 W’s is still most utilized by healthcare professionals from all over the world.


The first W in the mnemonic represents wind. This pertains to either pneumonia or atelectasis which causes complications in the lungs, thus the correlation with wind. In the instance that a fever develops within the first 24 to 48 hours after a surgery, then doctors should consider a problem with the lungs.

Pneumonia is one of the most common infections affecting the lungs, caused by the bacteria streptococcus pneumoniae. A lowered immune response is common post-operatively, and because pneumonia is particularly easy to contract when your immune system is down, it becomes one of the main dangers of the post-op condition.

If a medical professional observes a fever within the first 48 hours after a surgery, pneumonia might be one of the potential causes. However, if the patient presents symptoms incongruent with this type of infection, the doctor may consider atelectasis as the cause of the fever.

Atelectasis is defined as the closure or collapse of one lung, resulting in e reduced capacity for gas exchange. The condition is commonly unilateral, affecting only one side of the lungs.

Studies suggest that atelectasis is particularly common post-operatively for several reasons. Firstly, anaesthesia can compromise the ability of chest and abdominal muscles to contract, thus affecting a person’s breathing. Second, the inability to cough after a surgery can cause the accumulation of mucus, blocking parts of the airways.

Past research has correlated post-operative fever with atelectasis, however current studies suggest that there is no connection between the two. This is one of the main reasons why revisions have been made to the 5 W’s, with some versions only considering pneumonia as a possible reason for a fever occurring within the first 48 hours post-op.


A fever that develops 3 to 5 days after surgery could be indicative of a urinary tract infection – represented by the word water. One of the most common protocols across hospitals is the insertion of a Foley catheter prior to surgery. This is performed for sanitary reasons, as the patient may temporarily lose control of bladder function when anaesthesia is introduced into his or her system.

According to statistics, 75% of UTIs acquired in the hospital setting are caused by urinary catheters. Of course, as a case of UTI is caused by a bacterial agent, it’s necessary to administer antibiotics in order to eradicate the existing threat.

If a fever develops anywhere between 3 to 5 days after an operation, it’s possible to rule out lung infections or conditions in favor of a possible urinary tract infection.


When a patient develops a fever 5 to 7 days after a surgery, doctors may no longer consider either lung problems or UTI as possible causes. During this time, the causative factor responsible for the fever is most likely an infection of the wound, either superficial or deep.

Our bodies tend to increase temperature in the presence of an infection in an effort to fight it off. As certain bacteria can’t survive in hot temperatures, our system bumps up the heat in order to kill off what it can.

You’ll notice that the skin surrounding a post-operative wound might be slightly warm to the touch compared to the rest of your body. However, if the temperature continues to rise and starts to spread throughout the entire body, then it’s possible the wound may have become infected.

It’s vital that healthcare professionals act on this type of fever immediately, as infections of wounds can easily spread and cause sepsis – a potentially life-threatening state characterized by widespread bacteria and toxins.


The fourth W in the sequence means walking, and represents a deep vein thrombosis. This entry can also be taken to mean the presence of a pulmonary embolism.

A thrombosis is usually a cause for concern because it can result to a variety of complicated illnesses and even death. Commonly, these clots collect in deep veins that travel from the legs towards the heart, thus affecting a person’s gait. This is why the mnemonic uses the term walking.

In the presence of a DVT, patients are encouraged to avoid too much physical activity that could potentially dislodge the thrombus and cause it to travel to areas like the pulmonary veins. If this does occur, DVT then results to a pulmonary embolism which is considered a medical emergency.

Published studies dating back as far as the 60’s pointed out a correlation between DVT and increased body temperature. The reason behind the connection however is still unknown.

Nonetheless, a patient who develops a fever 5 days or more after a surgery might be suffering from a DVT. Some sources suggest that DVT causes fever 7-10 days post-operatively.

However, because the time-frame for DVT and a wound infection overlap, it’s the responsibility of the healthcare professional in-charge of the patient’s case to rule out one of the two.

Wonder Drugs

During a surgery, it’s impossible for doctors not to administer some sort of medication. These help prep the patient for the operation, either numbing the senses, normalizing certain vital signs, or keeping them stable during the procedure.

Sometimes, these drugs or blood products might not be compatible with a person’s system. So the body rejects the substances by developing a fever on top of a host of other symptoms such as chills, rigor, changes in heart rate, respiratory rate, and blood pressure, to name a few.

Often, these instances are considered a medical emergency, during which doctors have several options for treatment. In some rare cases however, fever may resolve within 30 minutes without any treatment.

But if the case is caused by allergic or anaphylactic reactions, doctors may have to provide several medications to help normalize the patient’s condition. Doctors are also prompted to anticipate renal failure, disseminated intravascular coagulation, and hypotension.

A fever caused by wonder drugs can occur anytime after a surgery. This is what makes it particularly tricky to determine, as the time-frame for this particular cause overlaps with all of the other four possible factors.

Properly assessing the situation and observing the signs and symptoms should help cancel out the causes to come up with proper and appropriate treatment.

Variations to the 5 W’s

Some other variations of the 5 W’s have surfaced over the years. While it’s still unknown who made the revisions, some medical practitioners choose to use the updated versions over the traditional because they consider it to be more reliable.

The most popular version of the 5 W’s includes two other possible causes – (W)abscess and waterway.

(W)abscess pertains to the infection of a space or organ, and usually occurs 5 to 7 days post-op. For most healthcare professionals, this item can be considered a subsection of the third W in the traditional guide – wound. However, it is important to note that the distinction lies in the fact that a fever caused by an infection of a space or organ does not necessarily involve the surgical incision, and may thus require a completely different treatment angle.

Waterway refers to a fever caused by a bloodstream infection. Otherwise called septicemia, this type of infection occurs when a bacterial infection elsewhere in the body makes its way into the bloodstream. This poses a particular threat as blood travels throughout the entire system, so any bacteria contained in the vessels can easily infect other parts of the body.

Bloodstream infections can occur anytime after a surgery. So medical practitioners are urged to carefully consider all the signs and symptoms before making a conclusion, as this causative factor does overlap with several others in terms of time frame.

In Closing

The 5 W’s of post-operative fever can definitely be a helpful tool to asses a patient’s healing. With this simple yet intelligent mnemonic, potential complications can be easily identified by taking into consideration nothing more than a fever and the time at which it occurs.

It is important however to remember to look at the bigger picture. Conditions can vary from person to person, and variations can be slight or pronounced. Assessing each patient as an individual case and using the mnemonic as nothing more than an ancillary guide can help you generate a more accurate diagnosis.


  1. Very profound

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